In the related art, multi-mode and multi-band wireless communication devices such as portable phones are being developed, and with this, the number of ports for switches that switch high-frequency signals tends to increase. Therefore, the number of pins on IC chips also increases.
In order to reduce the number of pins on this kind of IC chip, a serial-to-parallel converter, which converts serial data signals into parallel signals, is built in the IC chip.
Because the serial-to-parallel converter performs logic operations, which entail switching rectangular wave signals with values 0 and 1, the switching operations create high-frequency noise. If the high-frequency noise overlaps the frequency band of signals that are switched by the high-frequency switch within the IC chip, the high-frequency switch is adversely affected by the high-frequency switching noise.